A Notch toward Progenitor D(G)FRentiation: Defining a NOTCH-PDGFR axis in brown adipogenesis.

Brown adipocytes are found in several fat depots, however, the origins and contributions of different lineages of adipogenic progenitor cells (APCs) to these depots are unclear. In this issue of Developmental Cell, Shi et al. show that platelet-derived growth factor receptor ß (PDGFRß)-lineage and T-box transcription factor 18 (TBX18)-lineage APCs differentially contribute to brown adipogenesis across these depots.

Somatic PDGFRB activating variants promote smooth muscle cell phenotype modulation in intracranial fusiform aneurysm.

BACKGROUND: The fusiform aneurysm is a nonsaccular dilatation affecting the entire vessel wall over a short distance. Although PDGFRB somatic variants have been identified in fusiform intracranial aneurysms, the molecular and cellular mechanisms driving fusiform intracranial aneurysms due to PDGFRB somatic variants remain poorly understood. METHODS: In this study, single-cell sequencing and immunofluorescence were employed to investigate the phenotypic changes in smooth muscle cells within fusiform intracranial aneurysms. Whole-exome sequencing revealed the presence of PDGFRB gene mutations in fusiform intracranial aneurysms. Subsequent immunoprecipitation experiments further explored the functional alterations of these mutated PDGFRB proteins. For the common c.1684 mutation site of PDGFRß, we established mutant smooth muscle cell lines and zebrafish models. These models allowed us to simulate the effects of PDGFRB mutations. We explored the major downstream cellular pathways affected by PDGFRBY562D mutations and evaluated the potential therapeutic effects of Ruxolitinib. RESULTS: Single-cell sequencing of two fusiform intracranial aneurysms sample revealed downregulated smooth muscle cell markers and overexpression of inflammation-related markers in vascular smooth muscle cells, which was validated by immunofluorescence staining, indicating smooth muscle cell phenotype modulation is involved in fusiform aneurysm. Whole-exome sequencing was performed on seven intracranial aneurysms (six fusiform and one saccular) and PDGFRB somatic mutations were detected in four fusiform aneurysms. Laser microdissection and Sanger sequencing results indicated that the PDGFRB mutations were present in smooth muscle layer. For the c.1684 (chr5: 149505131) site mutation reported many times, further cell experiments showed that PDGFRBY562D mutations promoted inflammatory-related vascular smooth muscle cell phenotype and JAK-STAT pathway played a crucial role in the process. Notably, transfection of PDGFRBY562D in zebrafish embryos resulted in cerebral vascular anomalies. Ruxolitinib, the JAK inhibitor, could reversed the smooth muscle cells phenotype modulation in vitro and inhibit the vascular anomalies in zebrafish induced by PDGFRB mutation. CONCLUSION: Our findings suggested that PDGFRB somatic variants played a role in regulating smooth muscle cells phenotype modulation in fusiform aneurysms and offered a potential therapeutic option for fusiform aneurysms.

Inducible deletion of microRNA activity in kidney mesenchymal cells exacerbates renal fibrosis.

MicroRNAs (miRNAs) are sequence-specific inhibitors of post-transcriptional gene expression. However, the physiological functions of these non-coding RNAs in renal interstitial mesenchymal cells remain unclear. To conclusively evaluate the role of miRNAs, we generated conditional knockout (cKO) mice with platelet-derived growth factor receptor-ß (PDGFR-ß)-specific inactivation of the key miRNA pathway gene Dicer. The cKO mice were subjected to unilateral ureteral ligation, and renal interstitial fibrosis was quantitatively evaluated using real-time polymerase chain reaction and immunofluorescence staining. Compared with control mice, cKO mice had exacerbated interstitial fibrosis exhibited by immunofluorescence staining and mRNA expression of PDGFR-ß. A microarray analysis showed decreased expressions of miR-9-5p, miR-344g-3p, and miR-7074-3p in cKO mice compared with those in control mice, suggesting an association with the increased expression of PDGFR-ß. An analysis of the signaling pathways showed that the major transcriptional changes in cKO mice were related to smooth muscle cell differentiation, regulation of DNA metabolic processes and the actin cytoskeleton, positive regulation of fibroblast proliferation and Ras protein signal transduction, and focal adhesion-PI3K/Akt/mTOR signaling pathways. Depletion of Dicer in mesenchymal cells may downregulate the signaling pathway related to miR-9-5p, miR-344g-3p, and miR-7074-3p, which can lead to the progression of chronic kidney disease. These findings highlight the possibility for future diagnostic or therapeutic developments for renal fibrosis using miR-9-5p, miR-344g-3p, and miR-7074-3p.

The Notch-PDGFRß axis suppresses brown adipocyte progenitor differentiation in early post-natal mice.

De novo brown adipogenesis holds potential in combating the epidemics of obesity and diabetes. However, the identity of brown adipocyte progenitor cells (APCs) and their regulation have not been extensively explored. Here, through in vivo lineage tracing and mouse modeling, we observed that platelet-derived growth factor receptor beta (PDGFRß)+ pericytes give rise to developmental brown adipocytes but not to those in adult homeostasis. By contrast, T-box 18 (TBX18)+ pericytes contribute to brown adipogenesis throughout both developmental and adult stages, though in a depot-specific manner. Mechanistically, Notch inhibition in PDGFRß+ pericytes promotes brown adipogenesis by downregulating PDGFRß. Furthermore, inhibition of Notch signaling in PDGFRß+ pericytes mitigates high-fat, high-sucrose (HFHS)-induced glucose and metabolic impairment in mice during their development and juvenile phases. Collectively, these findings show that the Notch/PDGFRß axis negatively regulates developmental brown adipogenesis, and its repression promotes brown adipose tissue expansion and improves metabolic health.

The novel TERF2::PDGFRB fusion gene enhances tumorigenesis via PDGFRB/STAT5 signalling pathways and sensitivity to TKI in ph-like ALL.

Patients with Philadelphia chromosome-like acute lymphoblastic leukaemia (Ph-like ALL) often face a grim prognosis, with PDGFRB gene fusions being commonly detected in this subgroup. Our study has unveiled a newfound fusion gene, TERF2::PDGFRB, and we have found that patients carrying this fusion gene exhibit sensitivity to dasatinib. Ba/F3 cells harbouring the TERF2::PDGFRB fusion display IL-3-independent cell proliferation through activation of the p-PDGFRB and p-STAT5 signalling pathways. These cells exhibit reduced apoptosis and demonstrate sensitivity to imatinib in vitro. When transfused into mice, Ba/F3 cells with the TERF2::PDGFRB fusion gene induce tumorigenesis and a shortened lifespan in cell-derived graft models, but this outcome can be improved with imatinib treatment. In summary, we have identified the novel TERF2::PDGFRB fusion gene, which exhibits oncogenic potential both in vitro and in vivo, making it a potential therapeutic target for tyrosine kinase inhibitors (TKIs).

SCARB1-encoded circ _0029343 induces p73 splicing to promote growth and metastasis of hepatocellular carcinoma via miR-486-5p/SRSF3 axis.

Circular RNAs (circRNAs) exhibit essential regulation in the malignant development of hepatocellular carcinoma (HCC). This study aims to investigate the physiological mechanisms of circ_0029343 encoded by scavenger receptor class B member 1 (SCARB1) involved in the growth and metastasis of HCC. Differentially expressed mRNAs in HCC were obtained, followed by the prediction of target genes of differentially expressed miRNAs and gene ontology and kyoto encyclopedia of genes and genomes analysis on the differentially expressed mRNAs. Moreover, the regulatory relationship between circRNAs encoded by SCARB1 and differentially expressed miRNAs was predicted. In vitro cell experiments were performed to verify the effects of circ_0029343, miR-486-5p, and SRSF3 on the malignant features of HCC cells using the gain- or loss-of-function experiments. Finally, the effects of circ_0029343 on the growth and metastasis of HCC cells in xenograft mouse models were also explored. It was found that miR-486-5p might interact with seven circRNAs encoded by SCARB1, and its possible downstream target gene was SRSF3. Moreover, SRSF3 was associated with the splicing of various RNA. circ_0029343 could sponge miR-486-5p to up-regulate SRSF3 and activate PDGF-PDGFRB (platelet-derived growth factor and its receptor, receptor beta) signaling pathway by inducing p73 splicing, thus promoting the proliferation, migration, and invasion and inhibiting apoptosis of HCC cells. In vivo, animal experiments further confirmed that overexpression of circ_0029343 could promote the growth and metastasis of HCC cells in nude mice. circ_0029343 encoded by SCARB1 may induce p73 splicing and activate the PDGF-PDGFRB signaling pathway through the miR-486-5p/SRSF3 axis, thus promoting the growth and metastasis of HCC cells.

In the Rat Hippocampus, Pilocarpine-Induced Status Epilepticus Is Associated with Reactive Glia and Concomitant Increased Expression of CD31, PDGFRß, and Collagen IV in Endothelial Cells and Pericytes of the Blood-Brain Barrier.

In humans and animal models, temporal lobe epilepsy (TLE) is associated with reorganization of hippocampal neuronal networks, gliosis, neuroinflammation, and loss of integrity of the blood-brain barrier (BBB). More than 30% of epilepsies remain intractable, and characterization of the molecular mechanisms involved in BBB dysfunction is essential to the identification of new therapeutic strategies. In this work, we induced status epilepticus in rats through injection of the proconvulsant drug pilocarpine, which leads to TLE. Using RT-qPCR, double immunohistochemistry, and confocal imaging, we studied the regulation of reactive glia and vascular markers at different time points of epileptogenesis (latent phase-3, 7, and 14 days; chronic phase-1 and 3 months). In the hippocampus, increased expression of mRNA encoding the glial proteins GFAP and Iba1 confirmed neuroinflammatory status. We report for the first time the concomitant induction of the specific proteins CD31, PDGFRß, and ColIV-which peak at the same time points as inflammation-in the endothelial cells, pericytes, and basement membrane of the BBB. The altered expression of these proteins occurs early in TLE, during the latent phase, suggesting that they could be associated with the early rupture and pathogenicity of the BBB that will contribute to the chronic phase of epilepsy.

Tyrosine kinase inhibitor response of ABL-class acute lymphoblastic leukemia: the role of kinase type and SH3 domain.

ABSTRACT: Acute lymphoblastic leukemia (ALL) with fusions of ABL-class tyrosine kinase genes other than BCR::ABL1 occurs in ∼3% of children with ALL. The tyrosine kinase genes involved in this BCR::ABL1-like (Ph-like) subtype include ABL1, PDGFRB, ABL2, and CSF1R, each of which has up to 10 described partner genes. ABL-class ALL resembles BCR::ABL1-positive ALL with a similar gene expression profile, poor response to chemotherapy, and sensitivity to tyrosine kinase inhibitors (TKIs). There is a lack of comprehensive data regarding TKI sensitivity in the heterogeneous group of ABL-class ALL. We observed variability in TKI sensitivity within and among each ABL-class tyrosine kinase gene subgroup. We showed that ALL samples with fusions for any of the 4 tyrosine kinase genes were relatively sensitive to imatinib. In contrast, the PDGFRB-fused ALL samples were less sensitive to dasatinib and bosutinib. Variation in ex vivo TKI response within the subset of samples with the same ABL-class tyrosine kinase gene was not associated with the ALL immunophenotype, 5' fusion partner, presence or absence of Src-homology-2/3 domains, or deletions of IKZF1, PAX5, or CDKN2A/B. In conclusion, the tyrosine kinase gene involved in ABL-class ALL is the main determinant of TKI sensitivity and relevant for specific TKI selection.

Platelet-derived growth factor signaling in pericytes promotes hypothalamic inflammation and obesity.

BACKGROUND: Pericytes are a vital component of the blood-brain barrier, and their involvement in acute inflammation was recently suggested. However, it remains unclear whether pericytes contribute to hypothalamic chronic inflammation and energy metabolism in obesity. The present study investigated the impact of pericytes on the pathophysiology of obesity by focusing on platelet-derived growth factor (PDGF) signaling, which regulates pericyte functions. METHODS: Tamoxifen-inducible systemic conditional PDGF receptor ß knockout mice (Pdgfrb∆SYS-KO) and Calcium/calmodulin-dependent protein kinase type IIa (CaMKIIa)-positive neuron-specific PDGF receptor ß knockout mice (Pdgfrb∆CaMKII-KO) were fed a high-fat diet, and metabolic phenotypes before and 3 to 4 weeks after dietary loading were examined. Intracellular energy metabolism and relevant signal transduction in lipopolysaccharide- and/or platelet-derived growth factor-BB (PDGF-BB)-stimulated human brain pericytes (HBPCs) were assessed by the Seahorse XFe24 Analyzer and Western blotting. The pericyte secretome in conditioned medium from HBPCs was studied using cytokine array kit, and its impact on polarization was examined in bone marrow-derived macrophages (BMDMs), which are microglia-like cells. RESULTS: Energy consumption increased and body weight gain decreased after high-fat diet loading in Pdgfrb∆SYS-KO mice. Cellular oncogene fos (cFos) expression increased in proopiomelanocortin (POMC) neurons, whereas microglial numbers and inflammatory gene expression decreased in the hypothalamus of Pdgfrb∆SYS-KO mice. No significant changes were observed in Pdgfrb∆CaMKII-KO mice. In HBPCs, a co-stimulation with lipopolysaccharide and PDGF-BB shifted intracellular metabolism towards glycolysis, activated mitogen-activated protein kinase (MAPK), and modulated the secretome to the inflammatory phenotype. Consequently, the secretome showed an increase in various proinflammatory chemokines and growth factors including Epithelial-derived neutrophil-activating peptide 78 (C-X-C motif chemokine ligand (CXCL)5), Thymus and activation-regulated chemokine (C-C motif chemokine (CCL)17), Monocyte chemoattractant protein 1 (CCL2), and Growth-regulated oncogene α (CXCL1). Furthermore, conditioned medium from HBPCs stimulated the inflammatory priming of BMDMs, and this change was abolished by the C-X-C motif chemokine receptor (CXCR) inhibitor. Consistently, mRNA expression of CXCL5 was elevated by lipopolysaccharide and PDGF-BB treatment in HBPCs, and the expression was significantly lower in the hypothalamus of Pdgfrb∆SYS-KO mice than in control Pdgfrbflox/flox mice (FL) following 4 weeks of HFD feeding. CONCLUSIONS: PDGF receptor ß signaling in hypothalamic pericytes promotes polarization of macrophages by changing their secretome and contributes to the progression of obesity.

Cancer-Associated Fibroblasts Promote Lymphatic Metastasis in Cholangiocarcinoma via the PDGF-BB/PDGFR-ß Mediated Paracrine Signaling Network.

Patients with cholangiocarcinoma (CCA) with lymph node metastasis (LNM) have the worst prognosis, even after complete resection; however, the underlying mechanism remains unclear. Here, we established CAF-derived PDGF-BB as a regulator of LMN in CCA. Proteomics analysis revealed upregulation of PDGF-BB in CAFs derived from patients with CCA with LMN (LN+CAFs). Clinically, the expression of CAF-PDGF-BB correlated with poor prognosis and increased LMN in patients with CCA, while CAF-secreted PDGF-BB enhanced lymphatic endothelial cell (LEC)-mediated lymphangiogenesis and promoted the trans-LEC migration ability of tumor cells. Co-injection of LN+CAFs and cancer cells increased tumor growth and LMN in vivo. Mechanistically, CAF-derived PDGF-BB activated its receptor PDGFR-ß and its downstream ERK1/2-JNK signaling pathways in LECs to promote lymphoangiogenesis, while it also upregulated the PDGFR-ß-GSK-P65-mediated tumor cell migration. Finally, targeting PDGF-BB/PDGFR-ß or the GSK-P65 signaling axis prohibited CAF-mediated popliteal lymphatic metastasis (PLM) in vivo. Overall, our findings revealed that CAFs promote tumor growth and LMN via a paracrine network, identifying a promising therapeutic target for patients with advanced CCA.

Concurrent PTEN and PDGFRB Alterations Characterize Storiform Collagenoma.

Storiform collagenoma is a rare mesenchymal skin tumor that is composed of thickened collagen bundles arranged in a characteristic storiform pattern with a relatively hypocellular CD34-positive spindle cell component. Storiform collagenoma is most often sporadic, but multiple lesions can occur in Cowden syndrome, which is characterized by germline alterations in PTEN (phosphatase and tensin homolog) on chromosome 10. Here, we investigated the molecular pathogenesis of storiform collagenoma using a targeted next-generation DNA sequencing platform, including 5 sporadic cases and one case associated with Cowden syndrome. Recurrent PTEN alterations were identified in all cases, with biallelic PTEN inactivation observed in the case associated with Cowden syndrome and one sporadic case. Unexpectedly, we also identified recurrent activating mutations in the platelet-derived growth factor receptor beta ( PDGFRB ) gene. This included a missense substitution in the D5 Ig-like domain of PDGFRB in the Cowden syndrome-associated case. In addition, we report missense alterations in the juxtamembrane domain of PDGFRB in 4 of 5 (80%) sporadic cases, including mutations that have been previously described in sporadic myofibroma and myopericytoma. Therefore, we confirm the neoplastic nature of storiform collagenoma, we expand the spectrum of reported PDGFRB alterations in mesenchymal tumors and we suggest a possible collaborative role for PTEN and PDGFRB in the pathogenesis of storiform collagenoma.

Identification of distinct vascular mural cell populations during zebrafish embryonic development.

BACKGROUND: Mural cells are an essential perivascular cell population that associate with blood vessels and contribute to vascular stabilization and tone. In the embryonic zebrafish vasculature, pdgfrb and tagln are commonly used as markers for identifying pericytes and vascular smooth muscle cells. However, the overlapping and distinct expression patterns of these markers in tandem have not been fully described. RESULTS: Here, we used the Tg(pdgfrb:Gal4FF; UAS:RFP) and Tg(tagln:NLS-EGFP) transgenic lines to identify single- and double-positive perivascular cell populations on the cranial, axial, and intersegmental vessels between 1 and 5 days postfertilization. From this comparative analysis, we discovered two novel regions of tagln-positive cell populations that have the potential to function as mural cell precursors. Specifically, we found that the hypochord-a reportedly transient structure-contributes to tagln-positive cells along the dorsal aorta. We also identified a unique mural cell progenitor population that resides along the midline between the neural tube and notochord and contributes to intersegmental vessel mural cell coverage. CONCLUSION: Together, our findings highlight the variability and versatility of tracking both pdgfrb and tagln expression in mural cells of the developing zebrafish embryo and reveal unexpected embryonic cell populations that express pdgfrb and tagln.

PDGFRß Activation Induced the Bovine Embryonic Genome Activation via Enhanced NFYA Nuclear Localization.

Embryonic genome activation (EGA) is a critical step during embryonic development. Several transcription factors have been identified that play major roles in initiating EGA; however, this gradual and complex mechanism still needs to be explored. In this study, we investigated the role of nuclear transcription factor Y subunit A (NFYA) in bovine EGA and bovine embryonic development and its relationship with the platelet-derived growth factor receptor-ß (PDGFRß) by using a potent selective activator (PDGF-BB) and inhibitor (CP-673451) of PDGF receptors. Activation and inhibition of PDGFRß using PDGF-BB and CP-673451 revealed that NFYA expression is significantly (p < 0.05) affected by the PDGFRß. In addition, PDGFRß mRNA expression was significantly increased (p < 0.05) in the activator group and significantly decreased (p < 0.05) in the inhibitor group when compared with PDGFRα. Downregulation of NFYA following PDGFRß inhibition was associated with the expression of critical EGA-related genes, bovine embryo development rate, and implantation potential. Moreover, ROS and mitochondrial apoptosis levels and expression of pluripotency-related markers necessary for inner cell mass development were also significantly (p < 0.05) affected by the downregulation of NFYA while interrupting trophoblast cell (CDX2) differentiation. In conclusion, the PDGFRß-NFYA axis is critical for bovine embryonic genome activation and embryonic development.

Inhibition of PDGFRß alleviates endothelial cell apoptotic injury caused by DRP-1 overexpression and mitochondria fusion failure after mitophagy.

Kawasaki disease (KD), described as "mucocutaneous lymph node syndrome", affects infants and toddlers. Patients with KD suffer from an inflammatory cascade leading to vasculitis with a predilection for coronary arteries. While the symptoms and pathogenesis of KD have received more and more attention, the precise mechanisms are still debated. Researches show that endothelial dysfunction process in KD leads to arterial damage and affect clinical outcome. In this study, we constructed a Candida albicans water soluble fraction (CAWS)-induced KD murine model and penetrated investigating the mechanisms behind endothelial dysfunction. CAWS-induced mice presented remarkably elevated vascular endothelial cell growth factor (VEGF) levels. Abundant expression of VEGF was documented in all vessels that showed edema from acute KD. It has been reported that Platelet-derived growth factor (PDGF) co-expression normalizes VEGF-induced aberrant angiogenesis. Hyperexpression of PDGFRß was induced in the thickened medial layer and vascular endothelium of KD mice. Masitinib (Mas) is an oral tyrosine kinase inhibitor of numerous targets, which can selectively target PDGFR signaling. We set out to explore whether Mas could regulate coronary pathology in KD. Mas administration significantly reduced the VEGF-induced endothelial cells migration. NOX4 was activated in vascular endothelial cells to produce more ROS. Mitochondrial dysregulated fission and mitophagy caused by DRP-1 overexpression precipitated the arterial endothelial cells injury. Here, mitophagy seemed to work as the driving force of DRP-1/Bak/BNIP3-dependent endothelial cells apoptosis. In summary, how mitophagy is regulated by DRP-1 under pathologic status is critical and complex, which may contribute to the development of specific therapeutic interventions in cardiovascular diseases patients, for example Masatinib, the inhibitor of PDGFRß. FACTS AND QUESTIONS: Kawasaki disease causing systemic vasculitis, affects infants and toddlers. Coronary artery injury remains the major causes of morbidity and mortality. DRP-1 overexpression induces DRP-1/Bak/BNIP3-dependent endothelial cells apoptosis. PDGFRß was high-expressed in the thickened medial layer of CAWS-induced KD mice. Inhibition of PDGFRß signaling alleviates arterial endothelial cells injury.

Bone-derived PDGF-BB drives brain vascular calcification in male mice.

Brain vascular calcification is a prevalent age-related condition often accompanying neurodegenerative and neuroinflammatory diseases. The pathogenesis of large-vessel calcifications in peripheral tissue is well studied, but microvascular calcification in the brain remains poorly understood. Here, we report that elevated platelet-derived growth factor BB (PDGF-BB) from bone preosteoclasts contributed to cerebrovascular calcification in male mice. Aged male mice had higher serum PDGF-BB levels and a higher incidence of brain calcification compared with young mice, mainly in the thalamus. Transgenic mice with preosteoclast-specific Pdgfb overexpression exhibited elevated serum PDGF-BB levels and recapitulated age-associated thalamic calcification. Conversely, mice with preosteoclast-specific Pdgfb deletion displayed diminished age-associated thalamic calcification. In an ex vivo cerebral microvascular culture system, PDGF-BB dose-dependently promoted vascular calcification. Analysis of osteogenic gene array and single-cell RNA-Seq (scRNA-Seq) revealed that PDGF-BB upregulated multiple osteogenic differentiation genes and the phosphate transporter Slc20a1 in cerebral microvessels. Mechanistically, PDGF-BB stimulated the phosphorylation of its receptor PDGFRß (p-PDGFRß) and ERK (p-ERK), leading to the activation of RUNX2. This activation, in turn, induced the transcription of osteoblast differentiation genes in PCs and upregulated Slc20a1 in astrocytes. Thus, bone-derived PDGF-BB induced brain vascular calcification by activating the p-PDGFRß/p-ERK/RUNX2 signaling cascade in cerebrovascular cells.

Showcasing Different G-Quadruplex Folds of a G-Rich Sequence: Between Rule-Based Prediction and Butterfly Effect.

In better understanding the interactions of G-quadruplexes in a cellular or noncellular environment, a reliable sequence-based prediction of their three-dimensional fold would be extremely useful, yet is often limited by their remarkable structural diversity. A G-rich sequence related to a promoter sequence of the PDGFR-ß nuclease hypersensitivity element (NHE) comprises a G3-G3-G2-G4-G3 pattern of five G-runs with two to four G residues. Although the predominant formation of three-layered canonical G-quadruplexes with uninterrupted G-columns can be expected, minimal base substitutions in a non-G-tract domain were shown to guide folding into either a basket-type antiparallel quadruplex, a parallel-stranded quadruplex with an interrupted G-column, a quadruplex with a V-shaped loop, or a (3+1) hybrid quadruplex. A 3D NMR structure for each of the different folds was determined. Supported by thermodynamic profiling on additional sequence variants, formed topologies were rationalized by the identification and assessment of specific critical interactions of loop and overhang residues, giving valuable insights into their contribution to favor a particular conformer. The variability of such tertiary interactions, together with only small differences in quadruplex free energies, emphasizes current limits for a reliable sequence-dependent prediction of favored topologies from sequences with multiple irregularly positioned G-tracts.

Computational evidence for multi-layer crosstalk between the cadherin-11 and PDGFR pathways.

Various cell surface receptors play an important role in the differentiation and self-renewal of human mesenchymal stem cells (hMSCs). One example of such receptors are the cadherins, which maintain cell-cell adhesion and mechanically couple cells together. Recently, cadherin-11, which is a member of the type II classical cadherin family, has been shown to be involved in the fate commitment of hMSCs. Interestingly, cadherin-11 has no known intrinsic signaling activity and is thought to affect cell behavior via interactions with other cell surface receptors. Members of the platelet-derived growth factor receptor (PDGFR) family are hypothesized to be one of the interaction partners of cadherin-11. Experiments confirmed that PDGFR-α binding to extracellular cadherin-11 regions increases the PDGFR-α activity, whereas the interaction between PDGFR-ß and cadherin-11 suppresses the activity of the growth factor receptor. Cadherin-11 knockdown experiments also decreased cell proliferation. These interactions between cadherin-11 and PDGFRs indicate a crosstalk between these receptors and their downstream signaling activities but the nature of this crosstalk is not entirely known. In this study, we used a computational model to represent the experimentally proven interactions between cadherin-11 and the two PDGFRs and we inspected whether the crosstalk also exists downstream of the signaling initiated by the two receptor families. The computational framework allowed us to monitor the relative activity levels of each protein in the network. We performed model simulations to mimic the conditions of previous cadherin-11 knockdown experiments and to predict the effect of crosstalk on cell proliferation. Overall, our predictions suggest the existence of another layer of crosstalk, namely between ß-catenin (downstream to cadherin-11) and an ERK inhibitor protein (e.g. DUSP1), different than the crosstalk at the receptor level between cadherin-11 and PDGFR-α and -ß. By investigating the multi-level crosstalk between cadherin and PDGFRs computationally, this study contributes to an improved understanding of the effect of cell surface receptors on hMSCs proliferation.

Ligand-independent activation of platelet-derived growth factor receptor ß promotes vitreous-induced contraction of retinal pigment epithelial cells.

BACKGROUND: Epiretinal membranes in patients with proliferative vitreoretinopathy (PVR) consist of extracellular matrix and a number of cell types including retinal pigment epithelial (RPE) cells and fibroblasts, whose contraction causes retinal detachment. In RPE cells depletion of platelet-derived growth factor (PDGF) receptor (PDGFR)ß suppresses vitreous-induced Akt activation, whereas in fibroblasts Akt activation through indirect activation of PDGFRα by growth factors outside the PDGF family (non-PDGFs) plays an essential role in experimental PVR. Whether non-PDGFs in the vitreous, however, were also able to activate PDGFRß in RPE cells remained elusive. METHODS: The CRISPR/Cas9 technology was utilized to edit a genomic PDGFRB locus in RPE cells derived from an epiretinal membrane (RPEM) from a patient with PVR, and a retroviral vector was used to express a truncated PDGFRß short of a PDGF-binding domain in the RPEM cells lacking PDGFRß. Western blot was employed to analyze expression of PDGFRß and α-smooth muscle actin, and signaling events (p-PDGFRß and p-Akt). Cellular assays (proliferation, migration and contraction) were also applied in this study. RESULTS: Expression of a truncated PDGFRß lacking a PDGF-binding domain in the RPEM cells whose PDGFRB gene has been silent using the CRISPR/Cas9 technology restores vitreous-induced Akt activation as well as cell proliferation, epithelial-mesenchymal transition, migration and contraction. In addition, we show that scavenging reactive oxygen species (ROS) with N-acetyl-cysteine and inhibiting Src family kinases (SFKs) with their specific inhibitor SU6656 blunt the vitreous-induced activation of the truncated PDGFRß and Akt as well as the cellular events related to the PVR pathogenesis. These discoveries suggest that in RPE cells PDGFRß can be activated indirectly by non-PDGFs in the vitreous via an intracellular pathway of ROS/SFKs to facilitate the development of PVR, thereby providing novel opportunities for PVR therapeutics. CONCLUSION: The data shown here will improve our understanding of the mechanism by which PDGFRß can be activated by non-PDGFs in the vitreous via an intracellular route of ROS/SFKs and provide a conceptual foundation for preventing PVR by inhibiting PDGFRß transactivation (ligand-independent activation).

A novel subclonal rearrangement of the STRN3::PDGFRB gene in de novo acute myeloid leukemia with NPM1 mutation and its leukemogenic effects.

Chromosome translocations in the 5q31-33 region are associated with a range of hematologic malignancies, some of which involve the platelet-derived growth factor receptor beta (PDGFRB) gene. We report a case of acute myeloid leukemia (AML) with a mutation in the NPM1 gene (NPM1-mut AML) and a subclonal gene rearrangement involving the PDGFRB gene. We identified a novel fusion gene, STRN3::PDGFRB, resulting from t(5;14) (q32;q12) chromosomal rearrangement. Sequential FISH confirmed that ~15% of leukemic cells carried the PDGFRB gene rearrangement, which suggests that STRN3::PDGFRB is a previously unreported fusion gene in a subclone. Reverse transcription PCR (RT-PCR) and Sanger sequencing confirmed that the fusion gene consisted of STRN3 exon 7 fused to PDGFRB exon 11, resulting in a chimeric protein containing the coiled-coil domain of striatin-3 and the transmembrane and intracellular tyrosine kinase domains of the PDGFRB. The new protein exhibited distinct cytoplasmic localization and had leukemogenic effects, as demonstrated by its ability to transform Ba/F3 cells to growth factor independence and cause a fatal myelodysplastic/myeloproliferative neoplasm (MDS/MPN)-like disease in mice, which then transformant to T-cell lymphoblastic lymphoma in secondary recipients. Ba/F3 cells expressing STRN3::PDGFRB or ETV6::PDGFRB were sensitive to tyrosine kinase inhibitors (TKIs) and selinexor, but in vitro experiments showed that the combination of imatinib and selinexor had a marked synergistic effect, although only the imatinib alone group could prolong the survival of T-cell blast transformation recipient mice. Our findings demonstrate the leukemogenic effects of the novel fusion gene and provide insights into the clone evolution of AML, which can be influenced by therapy selection. Furthermore, our results provide insight into the potential therapeutic options for patients with this type of mutation, as well as the need for careful consideration of treatment selection to prevent undesirable side effects.